(a) Field of the Invention
The present invention relates to a method and a system for controlling a hybrid vehicle, and more particularly, to a method and a system for controlling a hybrid vehicle capable of supplying oil pressure to a transmission using an electric oil pump.
(b) Description of the Related Art
Generally, an automatic transmission is connected to an oil pump system to supply actuating oil pressure to an automatic transmission. The oil pump system includes at least one oil pump. In related art, an oil pump system which uses both a mechanical oil pump (MOP) and an electric oil pump (EOP) to supply actuating oil pressure to an automatic transmission has been developed.
Further, a hybrid vehicle of the related art uses a method for controlling an oil pump system which divides a driving section into a stop section, a low-speed section, and a high-speed section based on a driving state of a vehicle and selectively operates the mechanical oil pump and the electric oil pump. For example, the method for controlling an oil pump system operates only the electric oil pump in the stop section, simultaneously operates the mechanical oil pump and the electric oil pump in the slow-speed section, and operates only the mechanical oil pump in the high-speed section.
However, when at least two oil pumps such as the mechanical oil pump and the electric oil pump are used, production costs may substantially increase. Further, the mechanical oil pump operated by a driving torque of an engine may cause an adverse effect on fuel efficiency of the vehicle.
Meanwhile, when one of the mechanical oil pump and the electric oil pump is removed, the actuating oil pressure may be difficult to supply substantially stably to the automatic transmission. In particular, when using only the electric oil pump and when the supply of oil pressure to the automatic transmission is insufficient due to a failure of a solenoid, and the like, it may be difficult to perform a control for coping therewith. For example, as illustrated in FIG. 1, when a high voltage component or high voltage apparatus, high voltage load (e.g., air conditioner, electric oil pump, low voltage direct current-direct current (DC-DC) converter (LDC), inverter, and the like) which receives DC power from a high voltage battery 12 has failed, a main relay 14 connected to the high voltage battery 12 is turned off and thus a voltage of a DC link decreases to 0, such that an operation of all the high voltage components including the electric oil pump 20 may be terminated to stop a driving of the vehicle. Further, when the supply of oil pressure is insufficient, oil pressure required for the electric oil pump is set to be fixed to substantially high oil pressure, power for driving the electric oil pump may be wasted and the components may be damaged.
The above information disclosed in this section is merely for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.